netdev - Re: [PATCH] r8169: Reduce looping in the interrupt handler.

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Date:	Wed, 26 Aug 2009 13:02:58 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	David Dillow <dave@...dillows.org>
Cc:	Francois Romieu <romieu@...zoreil.com>,
	Michael Riepe <michael.riepe@...glemail.com>,
	Michael Buesch <mb@...sch.de>,
	Rui Santos <rsantos@...popie.com>,
	Michael B??ker <m.bueker@...lin.de>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] r8169: Reduce looping in the interrupt handler.

David Dillow <dave@...dillows.org> writes:

> On Wed, 2009-08-26 at 09:56 -0400, David Dillow wrote:
>> On Wed, 2009-08-26 at 00:58 -0700, Eric W. Biederman wrote:
>> > diff --git a/drivers/net/r8169.c b/drivers/net/r8169.c
>> > index 3b19e0c..2214945 100644
>> > --- a/drivers/net/r8169.c
>> > +++ b/drivers/net/r8169.c
>> 
>> > +
>> > +		/* Ignore the parts of status that reflect more than
>> > +		 * the enabled interrupts.
>> > +		 */
>> > +		smp_rmb();
>> > +		if (!(status & tp->intr_mask & tp->intr_event))
>> > +			break;
>> >  	}
>> 
>> This looks like an odd construct, since we're just about to go back the
>> while condition up top -- why not just mask it here and let the loop
>> handle it naturally?
>
> Never mind, I see what you are doing -- avoiding a false loop if we get
> status == 0xffff. I still don't like the aesthetics of it, but it makes
> sense, and I'll blame it on the card. :)
>
> I should really get some caffeine before posting...  

It is a bit weird but it also means we aren't playing silly games
with status inside the loop.  So if we go through the loop we ack
everything in status.

Eric

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